The Earth’s magnetic field is not about to flip

New modelling suggests north and south will remain that way for now.

Credit: iStock

It’s OK, you can relax now. Despite frequent speculation and dire predictions, the Earth’s magnetic field is not about to reverse itself.

Over a long geological scale, the planet’s north and south poles have flipped around on average of every 300,000 years. These polarity reversals are not anomalies, but the inevitable consequence of having a solid iron core surrounded by a fluid layer of hot, liquid metal.

Be that as it may, however, a field reversal today, given the amount of technology that takes magnetic orientation as a fundamental, could have significant and severe circumstances.

The last flip occurred 780,000 years ago, so the next one is well overdue, leading overexcited doomsday advocates to predict that a polarity apocalypse is imminent.

Recent wobbles

A team led by geomagnetism expert Richard Holme of the University of Leeds in the UK calculated the likelihood of a magnetic field reversal, using data arising from the two most recent “excursions” – periods during which the field essentially wobbles, but then returns to normal.

These occurred 41,000 years ago – a phenomenon known as the Laschamp excursion – and 34,000 years ago – dubbed the Mono Lake event.

Information for the two excursions was then compared with current readings that show the magnetic field has been weakening over the past two centuries. The study also took into account a second contemporary phenomenon, an area of weakened magnetism stretching from Chile to Zimbabwe, known as the South Atlantic Anomaly (SAA).

Holme and his colleagues found that magnetic field conditions broadly similar to the ones now in play were evident 49,000 and 46,000 years ago. However, in both cases accompanying anomalies akin to the SAA were much stronger.

Polar reversal

These phenomena continued to strengthen, leading to the Laschamp and Mono Lake wobbles, but not to reversals.

“There has been speculation that we are about to experience a magnetic polar reversal or excursion,” explains Holme.

“However, by studying the two most recent excursion events, we show that neither bear resemblance to current changes in the geomagnetic field and therefore it is probably unlikely that such an event is about to happen.

“Our research suggests instead that the current weakened field will recover without such an extreme event, and therefore is unlikely to reverse.”

About the Author

Andrew Masterson
Andrew Masterson is editor of Cosmos.

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